Electrode assembly for electrical discharge devices



Dec. 19, 1950 H vlll I I l l n l Illlllllnlhlfullllllll IN VENTOR EJ.WALSH WALSH E. J. ELECTRODE ASSEMBLY FOR ELECTRICAL DISCHARGE DEVICESFlled Aug 26, 1948 FIG 4 44 5 2/ I I fi I I 2/ /9 /4 /5 I8 23 ATTORNEYPatented Dec. 19, 1950 ELECTRODE ASSEIWBLY FOR ELECTRICAL DISCHARGEDEVICES Edward J. Walsh, Tenafly, N. J assignor to Bell TelephoneLaboratories, Incorporated, New York, N. Y., a corporation of New YorkApplication August 26, 1948, Serial No. 46,320

8 Claims.

This invention relates to electron discharge devices and moreparticularly to electrode assemblies and the method of fabricating theseassemblies for such devices.

The static characteristics of electronic discharge devices determine thescope of use and the efficiency of operation in low frequencyapplications. However, the requirements encountered in the very high andultra-high frequency ranges, such as the 100- to SOO-megacycle rangeimpose conditions which can only be satisfled by extremely precisemechanical correlation of the elements to produce the essentialelectrical constants whereby the highest efficiency is attained. Themost important characteristic for general use is the transconductance.The transconductance depends on the spacing between the cathode, controlgrid, and screen grid, the diameter of the grid wire, the spacingthereof, the electrode area and the potentials applied to theelectrodes. In order to attain a high transconductance, it is necessaryto reduce the diameter of the control-grid lateral wires to a pointwhere the wire is not self-supporting when wound in grid form.Therefore, the fine fragile wire must be wound on a support whichmaintains the collateral relation of grid and cathode constant at thevery close spacings, for example at the order of two mils.

In order to attain the close, precision relationship between electrodesurfaces and maintain mechanical stability of the system where fine gridlateral wires, on the order of 0.3 mil in diameter, are employed, it isimperative that some grid support be employed. The grid supports of theprior art, however, have not been satisfactory in the smaller tubessince a support of the size necessary to attain the required mechanicalstability has required relatively large electrode spacing and has addedundesirable capacitances to the support a plurality of electrodesections which are fabricated thereon. The electrode sections aresupported, with their effective surfaces parallel, from conductive studsprojecting from the base sheet. The wire grids of this assembly arefabricated on the base sheet on pairs of coplanar rods so connected tothe studs that the outermost edges of each pair define a plane parallelto and critically spaced from the next adjacent electrode. Grid lateralsare mounted by winding wire around the sheet and over the outermostedges of these rods, securing the winding to these outermost edges, andcutting away all but the wire extending between the rods. A plurality ofgrids may thus be constructed one over the other in very closerelationship. When the final grid has been fabricated on eachsubassembly, the two subassemblies are connected together and secured bysome convenient method.

While the description and drawings disclose an electrode structurecomposed of two subassemblies it is to be understood that this is merelyillustrative and a complete electrode assembly might be fabricated on asingle base without departing from the spirit of this invention.

The invention will be more clearly set forth in the following detaileddescription of the embodiment disclosed in the accompanying figures inwhich:

Fig. '1' is a perspective view of a multielement discharge deviceembodying the features of this invention, with a portion of the vesselbroken away to show the electrode structure;

Fig. 2 shows an elevation of the upper portion of the electrodeassembly;

Fig. 3 is a perspective view of the upper portion of one of thesubassemblies of the discharge device of Fig. 1 showing a portion of theelectrode structure in detail; and

Fig. 4 is a plan View of a pair of partially completed assemblysections, having portions of the structure omitted for clarity andshowing one method of mounting the grid laterals.

Referring to the drawing, an electron discharge device of micro-midgetdimensions embodying features of this invention is disclosed in Fig. 1wherein an electrode assembly H is mounted in an envelope l2. Thisassembly is made up of two sections of the type shown in Fig. 3 wheresheet member l3 of suitable insulating material forms a rigid base uponwhich is fabricated a plurality of parallel electrode sections, theseparations of which are determined by their spacing from the base 13 asa reference plane. The embodiment illustrated is a tetrode comprising ananode I4 supported on a rod I5 which is welded to a pair of conductivestuds I6 (only the upper studs appearing in Figs. 2 and 3). Adjacent theanode and critically spaced therefrom as determined by the height of thespacer projections I'I against which the side rods I8 are abutted andbythe diameter ofv the side rods, is the screen gridil9. The screen gridside rods I8 are welded to pairs of studs 20 located adjacent the spacerprojections I1. 2| is positioned next to the screen grid on side rods 22mounted as those of the screen. grid-:on pairs of conductive studs 23and abutted against spacer projections 24.

A filamentary cathode 25':is shown-supportedon one of the assemblysections from studs 25 projecting from the base I3. No spacenmeans hasbeen shown associated with the cathode, its position relative to thecontrol grid being determined by a removable jig. However, spacers ofthesame type asprojections l1 and 24might be'employed here.- Asanalternative method of cathode support, transverseend spacers ofconventional form might be-employed, such an arrangement taking the formof sheet mica spacers which might he slipped over the ends of the gridside rods 18 and 22 of each. subassembly after theyhave been assembled.A cathode of either a directly or an indirectly heated type might besupported centrally between the control grid sections from thesespacers.

Pairs of interlocking studs 2'! and tubes 28 mounted on the corners ofbase I3 are employed to connect two of the subassemblies as shown inFig; 2. The separation of the subassemblies is determined by the'lengthof the tubes 28 which are slid over their mating studs 27 so that theirends bear against the base It of the associated subassembly; Themechanical stability of the system is maintained by welding the tubes onthe studs.

The structure described above is especially adapted for simplicity ofmanufacture while maintaining high degree of "accuracywith smallelectrode spacings. The subassembly sections are-built up separately,base I 3 being made up with the studs -Ifi,"2!l,'23,-2t and 21 and thetubes 28 mounted thereon, and the electrodes are fabricated on thesestuds. In the case of a base adapted-for convenient molding, one ofglass or ceramic, the studs and tubes can be molded in the base andintegral spacer protuberances I! and 2 3 can-be formed in a singlemolding operation. Since the'height of the spacers is critical indetermining the electrode spacings each is ground to the proper heightafter being mounted on the base and prior to the fabrication of any ofthe electrodes. Then the anode support I5 is welded to the anode studsl6; its height from the plane surface of the base beingdetermined by ajig, and the anode I 4 is secured to the support rod-parallel to thebase. Next the two screen grid side rods I8 are welded to the screengrid studs 20 so that their. edges outermost; from the base define aplane parallel to that of the anode and criticallyspaced therefrom. Thespacing in the embodiment disclosed being determined by the height ofthe spacers I'I plus the diameter of the side rods, however, the resultcould be accomplished by positioning the side rods with removable jigsduring the welding operation or by employing side rods having athickness equal to the desired spacing of the grid from the base so thatthey could be secured flush against the plane surface of the base-withtheir outermost edges A control grid 1 defining a plane properly spacedfrom the anode. Screen grid laterals 29 are then mounted on the siderods by mounting the base I3 and the structure thereon in a windingmachine and winding wire suitable for laterals around the whole assemblso that it lays across the grid side rods I8 and extends around the backof the base I3. The lateral wires are then secured to the side rods bywelding or brazing, one method being to-plate the side rods with abrazing medium such as gold prior to their mounting and passing aheating current through only one rod at a time to'braze the laterals tothe rod, the heat produced in one rod being so slight as to cause nothermal distortion in the electrode assembly. The portion of the windingwhich does not extend between the side rods is then cut away and thecontrol grid fabricated in the same manner as the screen grid, bymounting side rods 22 on studs 23 to define with their outermost edges aplane parallel to. and critically spaced from the screen grid, windingthe grid laterals on the rods, securing them thereto, and cutting awaythe inefiective portions of the wires. The final step before assemblyofthe two sections is to mount the cathode upon one of the sections,this being done by welding the ribbon-like member 36 on the cathode studZfi-so that its outermost flat surface is parallel to the plane of thebase and is critically spaced from the base to determine the cathode tocontrol grid separation, and then welding the-cathode filaments to theoutermost surface of the member 38.

The two half sectionsare then joined as described heretofore, thev stud27 of each section being slipped into and welded in.the mating tube 23of the other section.

, Fig. 3 illustrates one method of construction which can beconveniently employedin fabricating subassemblies of the electrodeassembly of this invention. The connecting studs 21 and tubes 28 havebeen omitted from the drawing for purposes of clarity. In thisembodiment the studslt, 20 and 23 extend continuously through andmutually support a pair of spaced parallel base members l3. With such anarrangement, electrode sections are-fabricated back to back. Two gridscan be wound in a single winding operation by mounting a set of gridside rods on eachbase, placing the connected subassemblies in awindingmachine, and winding the structure with grid lateral wire so that thewire lays across the outermost edges of .therods of both, securing thelaterals to. the rods in the manner set forth. heretofore, and-removingthat portion of. thewire which extends betweenrods of the twosubassemblies. The. drawing shows completed screen grid sections, andcontrol grid sections which have not been trimmed of the excessivewireextending around the edges of the bases I3. When the grid structureshave been completed the connecting portion of the studs can be severedas indicated at 3| and the sections connected in a structure asdisclosed in Fig. 2..

The complete assembly is mounted in the envelope I2 on rods 32 extendingfrom suitable pins 33 in the envelope press 34. Straps 35 are connectedto the portions of the appropriate studs I6, 26, 23 and 26 projectingfrom 'the rear of the support bases I3, these straps extending from thestuds of each electrode section to leadin wires 36 sealed in the press3:3 or from only one stud of each electrode, in the latterarrangementslnot shown) a supplementary strap extending between theprojecting portion of the studs of the corresponding electrode sectionsof each subassembly must be used to connect these sections.

The structure resulting from this construction provides close electrodesspacing without the need of piece parts having critical fits since theelectrodes are built up on the mechanically stable base by using jigs,thereby making tubes of small dimensions practicable. It is to be notedfurther, that the grid wires can be conveniently aligned, as shown inFig. 2, so that the control grid may act as a shield for the screen gridto reduce screen grid current and prolong the life of the tube. Althoughthe electrodes of the tube are shown and described as being mounted oninsulating members, it is within the province of the invention to mountthem on metallic or conducting base members (not shown), the studs beinginsulatively mounted therein as by glass beads.

The above description is to be taken as illustrative only and not in alimiting sense the scope of the invention being set forth in thefollowing claims.

What is claimed is:

1. An electrode assembly for an electron discharge device, comprising abase member, studs projecting from said base member, spacers projectingfrom said base member, and electrodes abutted against said spacers andsecured to said studs in parallel relationship with each other and saidbase member.

2. An electrode assembly for an electron discharge device, comprising abase member, conductive studs extending through said base, a pair ofcoplanar conductive rods electrically and mechanically connected to saidstuds in parallel relationship with said base member, and grid lateralssecured to said rods.

3. An electrode assembly for an electron discharge device, comprising abase member, conductive studs extending through said base member,conductive rods electrically and mechanically connected to said studs,said rods arranged in coplanar pairs, each pair having its outermostedge define a plane parallel to and critically spaced from the plane ofsaid base, and grid laterals secured to each coplanar pair of rods.

4. An electrode assembly for an electron discharge device, comprising aninsulating base, conductive studs extending through said base,

' spacers mounted on said base, a plurality of conductive rods eachelectrically and mechanically connected to certain of said studs andabutting said spacers, said rods arranged in coplanar pairs, each pairhaving its outermost edge define a plane parallel to and criticallyspaced from the plane of said base, and grid laterals secured to each ofsaid coplanar pair of rods.

5. An electrode assembly for an electron discharge device, comprising apair of spaced parallel base members, studs projecting from the adjacentfaces of each of said base members, and parallel electrodes on each basemember supported from said studs in parallel relationship with said basemember.

6. An electrode assembly for an electron discharge device, comprising apair of plane parallel base members, conductive studs extending througheach of said base members, conductive rods on said studs on the adjacentfaces of said base members, said rods arranged in coplanar pairs, eachpair having its outermost edge define a plane parallel to and criticallyspaced from the plane of its base member, and grid laterals secured toeach coplanar pair of rods.

7. An electrode assembly for an electron discharge device, comprising apair of plane parallel base members, conductive studs extending througheach of said base members, spacers on each of said base members, ananode section mounted on the adjacent faces of each of said basemembers, coplanar pairs of conductive rods supported from said studs andabutting said spacers on the adjacent faces of each of said basemembers, each pair of said rods having its outer edges parallel to thesurface of its associated anode section and critically spaced there--from, grid laterals secured to each coplanar pair of said rods, and acathode supported between said base members.

8. An electron tube, comprising an envelope, a plurality of electricalconductors extending through the wall of said envelope, a base memberwithin said envelope, conductive studs extending through said basemember, conductive straps extending from said electrical conductors tosaid studs mechanically supporting said base member, and electrodessecured to said studs in parallel relationship with each other and saidbase member.

EDWARD J. WALSH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,472,505 Trimble Oct. 30, 19231,668,016 Hauschild May 1, 1928 1,799,850 Hendry Apr. 7, 1931 1,923,686Pidgeon et a1 Aug. 22, 1933 2,310,822 Wheeler Feb. 9, 1943 2,347,262Herzog Apr. 25, 1944 2,395,835 Bareiss Mar. 5, 1946 2,431,020 BinnewegNov. 18, 1947 2444.740 Jonker July 6, 1948

